Comet C/1997O1 Tilbrook
Justin Tilbrook from Clare, South Australia, reports a visual discovery of a comet on July 22.43 UT with a 20-cm reflector. Justin is a variable star observer and he discovered the comet while was observing TV Corvi when he saw a 10th mag “blob” of 70'' in diameter. Several minutes later he saw that the object had moved. One day later Gordon Garradd (from Loomberah) confirmed the comet using a 25-cm reflector+CCD, the images showed a little fuzzy of 2' without tail. IAU Circular 6705 announced the discovery on July 23 while a preliminary orbit announced in IAUC 6707 showed the comet was close to perihelion at about 1.4 AU from the Sun and a similar distance from the Earth. If the comet had been 3 months earlier, it would have been visible in 7x50 binoculars from the Earth.
Here are the orbital elements of the comet from 15 observations, July 23-24:
T = 1997 July 16.560
Peri. = 339.104
Node = 231.329
q = 1.38550 AU
Incl. = 114.115
The brightness evolution can be described by the formula m = 8.5m + 5×log D + 5×log r with this light curve:
Picture of C/1997O1 taken by Justin, using a 35-mm camera with a 200-mm zoom lens and 400ASA Fujicolor print film; on the evening of 1997 July 26 (10:45 UT). The camera was hand-guided for an exposure lasting 10 minutes, to capture this faint image of Comet Tilbrook.
Comet Tilbrook image taken by Akimasa Nakamura on 1997 July 24.47 UT
with a 60-cm Reflector f/6.